A method for monitoring the patient's teeth positioning, including the following steps: a) less than three months after the start of an orthodontic treatment, producing an initial reference model of the patient's arches, and, for each tooth, defining, from initial reference model, a tooth model; b) acquiring at least one updated image of the arches, under actual acquisition conditions; c) analyzing each updated image and producing an updated map relative to a piece of discriminating information; d) optionally determining rough virtual acquisition conditions that approximate the actual acquisition conditions; e) searching each updated image for a final reference model corresponding to the teeth's position during the updated image's acquisition, and; f) for each tooth model, comparing the tooth model's positions in the initial reference model and in reference model obtained at the end of the preceding steps, in order to determine movement of the teeth between steps a) and b).